Yamaha International issued their service news # 169 to the dealers in 1965. This explains that gearbox oil should NEARLY ALWAYS BE FILLED INTO THE GEARBOX and NOT INTO THE CLUTCH HOUSING. See the attached original Service News for details.

PLEASE NOTE: YOU CAN SEE WHEN YOU FILL OIL INTO THE CLUTCH HOUSING OF THESE MODELS, THE CLUTCH ALWAYS HAS TOO MUCH OIL AND THE GEARBOX NOT ENOUGH...........! (EXCEPT FOR THE YG AND OTHER MODELS ON THE L.H. PICTURE).